Fetch all properties when querying via a base interface.

[sylv1-corre]

Hello,

Having the following object models (I am using Kotlin):

interface Movie {
    val id: String
    val name: String
}

@Node("AnimationMovie")
class AnimationMovie(@Id override val id: String, override val name: String, val studio: String): Movie

@Node("Cinema")
class Cinema(@Id val id: String, val name: String,
             @Relationship("Plays", direction = Relationship.Direction.OUTGOING) val plays: List<Movie>
)

Along with the following repository:

interface CinemaRepository: Neo4jRepository<Cinema, String>

My database is setup as follows:

CREATE (:AnimationMovie {id: 'movie001', name: 'movie-001', studio: 'Pixar'})<-[:Plays]-(:Cinema {id:'cine-01', name: 'GrandRex'})

The cinema object returned by cinemaRepository.findAll() doesn't contain any movie in the plays field. If that field is declared as List<AnimationMovie> instead of List<Movie>, it works as expected and the relation is fulfilled... But I really want to be able to play different kinds of movies !

If I add a Movie label to the AnimationMovie (as in CREATE (:Movie:AnimationMovie {id: 'movie001', name: 'movie-001', studio: 'Pixar'})<-[:Plays]-(:Cinema {id:'cine-01', name: 'GrandRex'})), I get the following error:
Failed to instantiate [Movie]: Specified class is an interface

spring-data-neo4j version: 6.0.8

Any help would be highly appreciated !

Sylvain

[michael-simons]

Hi @sylv1-corre thanks for the ticket and the complete description.

Interfaces are allowed in an inheritance hierarchy since 62496fc which was part of 6.0.8, which is what you are using.

Please have a look at the documentation: A note on class hierarchies, you have something like Listing 12.

You need to add a common label to your base interface like this

@Node
interface Movie {
    val id: String
    val name: String
}

I have added a test for your scenarios (in Java, though), please see #2ed43e97b59add0be466ff8bbf212133064f7cce

Please let us know if this helps.

[michael-simons]

It seams that Kotlin behaves differently… Needs some more investigation.

[michael-simons]

For whatever reason Kotlin seems to be less eager to add the concrete class AnimationMovie to the mapping context, therefore it cannot be found and we try to instantiate the interface.

You could define a repository for it to load it or do something like this in a @Configuration class:

@Bean
fun neo4jMappingContext(@Autowired neo4JConversions: Neo4jConversions): Neo4jMappingContext {
	val f = Neo4jMappingContext(neo4JConversions)
	f.setInitialEntitySet(setOf(KotlinCinema::class.java, KotlinMovie::class.java, KotlinAnimationMovie::class.java))
	return f
}

Or extend from AbstractNeo4jConfig and specify the initial packages to scan

override fun getMappingBasePackages(): Collection<String?>? {
	return setOf(Inheritance::class.java.getPackage().name)
}

both approaches work for me.

However, I did spot a bug in what attributes we select based on the interface, which needs to be fixed.